C/L WB/WOT OEM ECUs...

[Garfield Willis]

On Fri, 7 Apr 2000 01:12:31 -0400, "nacelp" <nacelp at bright.net> wrote:

>I got several ideas, the basic question is to kludge or not to kludge.

OK, to K or not to K, that is the question. (Sorry, I couldn't
resist...)

>... tps interception ...

or...

>  ...getting into the calibration file, and setting the PE
>enable to 99%. and that should prevent the PE mode.

I take it we could refer to this as "major PE-enable/disable tweaks"?

So we have two mechanisms on the table so far. (1) is to intercept the
TPS signal, which is almost always used to flag/force PE modes, and then
we attempt to prevent them, by faking a false TPS input, and/or (2) to
systematically disable PE as much as the cal tables will allow.

OK, wellNgood, I understand the overall concept, but...What I'd like to
understand further is, for say an example OEM/GM ECM, is there a bit
that says "past this parametric point/level (TPS or MAP or whatever),
enable PE (aka go to O/L)"? The real question to me seems to be how MUCH
authority can we get over O/L vrs. C/L; not so much whether we can force
it without exception. That's why I'm asking cases-by-cases.

For example, we don't really care if there's no way to prevent the
coolant temps, below a certain value, forcing O/L and major enrichment.
On the contrary, we want that! We therefore don't need to worry about
intercepting these temp sensor inputs. Just let them be, and if they
force the ECU into O/L, no harm done; since actually we WANT them to go
to major O/L enrichments in these cold regimes.

But what we MUST accomplish for this concept to work (i.e., taking OEM
ECUs into WOT C/L), is to be able to thwart the normal excursion of the
ECU into O/L when either the TPS or MAP/MAF suggests we should
'normally' go to tables. I can readily see how interception of TPS could
be accomplished, BUTTTTTTT how about the ECU's normal transition to O/L
when the load/MAP/MAF exceeds a certain level? Can we/should we
intervene there? Reason I fear this is more problematic, is that we may
not be able to just FAKE or fudge the load inputs, otherwise we lose
needful accel and other transient enrichments that ARE really needed,
because relying on the AFR feedback alone, may be too slow/sloppy (given
that all we are getting is bang-bang controller response times; hey,
even WITH tightly servo'd C/L O2 sensing, FelPro still allows O/L
enrichment during major load/TPS excursions). What would be IDEAL (I'm
dreamin here, so bear with me), is that we could control via cal table
settings, the parametric limits of each of these inputs (or their
derivatives/rates-of-change), be they TPS or MAP/MAF, so that we could
say, beyond a certain level/rateOchange, GO to O/L and apply enrichment
table values, but whenever these inputs settle below these extreme
transient levels, then return to C/L and follow the "commanded AFR" (aka
the stoich-crossing setpoint we fake/program using WB sensing).

If we can do this across the board with most all key inputs in a
table-driven manner, we CAN control when we KEEP to C/L and follow the
WB O2 sensor, and at all the other times, we not only LET, nay...but
DESIRE the ECU to use it's enrichment tables to control O/L the mix. For
example, we WANT to ignore the WB O2 sensing when we're in
cold-crank/start and during warm-up. We also WANT to ignore the WB O2
sensing when someone transitions from 0 TPS to F/S TPS in a
quarter-second, and use the table-driven enrichments. Same goes with
rapid load excursions. If we can control via cal tables just WHEN we
want to go to C/L, then we'll have cracked this cookie, and ushered in a
new age of WB AFR control, where it counts most.

It's good (or at least OK) to have O/L PE dumping safety-measures of
fuel during a major power-up, during the first few fractions of a
second; but if after those transients, we can accomplish forcing the ECU
to lock on to a nice tight C/L 12.5AFR lets say, during the longer
period of major acceleration, then we will have accomplished something
quite useful. Because once we can control the AFR precisely during major
power phases, we'll be able to test just EXACTLY what AFR is indeed
optimum for acceleration/load, and then lock that in via C/L AFR
feedback/programming. No more FelPro or Motec envy. :)

If this can be accomplished within OEM ECUs, via cal table changes and
sensor intercepts alone, where needed, without resorting to 'custom' ECM
code changes, we've really met a horizon.

Thanks Bruce for the spark; I'd say as an mere EE, that sensor
intercepts should/can be viewed as very minor irritations easily
accomplished. What we need to determine next is how much authority can
be accomplished via PE-mode programming/disabling, and whether a combo
of your two suggestions could possibly accomplish the whole end game. If
so, methinks it's possibly fairly major doo-doo. :)  Anyone else have
further suggestions/comments/caveats? Speak up, pulleze.

Gar


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